1. Field of the Invention
This invention relates to air guns or filament draw nozzles used for the production of spun bonded nonwoven fabrics.
2. Description of the Prior Art
In the production of nonwoven webs from continuous filaments air guns or filament draw nozzles are commonly used to direct the filaments to the desired web forming location. Compressed air is generally supplied to the nozzles to serve as an entraining medium for the filaments. Examples of prior art filament draw nozzles are disclosed in Kinney U.S. Pat. No. 3,338,992, which issued Aug. 29, 1967; Kinney U.S. Pat. No. 3,341,394, which issued Sept. 12, 1967; Dorschner et. al. U.S. Pat. No. 3,655,862, which issued Apr. 11, 1972; Dorschner et al. U.S. Pat. No. 3,692,618, which issued Sept. 19, 1972; and Reba U.S. Pat. No. 3,754,694, which issued Aug. 28, 1973.
Prior art draw nozzles used for the production of nonwoven webs have a number of shortcomings, being generally characterized by their relatively complex design, often incorporating numerous parts, which results in high replacement cost and problems in maintaining the accurate alignment of parts. This latter problem can lead to asymmetric air flows which create swirl and thus roping of the filaments being conveyed by the nozzles. In addition, prior art nozzle constructions are often prone to plugging and wear problems and require high air pressure to operate. Thus, their operation is energy intensive and costly. Prior art draw nozzles also characteristically generally are difficult to thread initially and have relatively low fiber entrainment capacities due in large part to the fact that they commonly incorporate fiber feed tubes having relatively small internal diameters. Further, prior art draw nozzles, due to their complexity of construction, do not readily adapt themselves to internal vacuum monitoring, a desirable feature for filament flow control.
It is therefore an object of the present invention to provide a filament draw nozzle which eliminates, or at least minimizes, the aforesaid shortcomings of prior art arrangements.